1. Field of the Invention
The present invention relates to a process for the preparation of 3-fluoro-2-(fluoromethyl)-propene (see formula (I)) ##STR1## which can also be called difluoroisobutylene, and to the new compound 3-fluoro-2-(chloromethyl)-propene (see formula (II)) ##STR2## which can also be called fluoro-chloro-isobutylene.
2. Background Information
3-Fluoro-2-(fluoromethyl)-propene is a useful intermediate product for syntheses in organic chemistry, for example, in the fields of dyestuffs, pharmaceuticals, plant protection agents, plastics and textile and plastics auxiliaries. This particular olefin is particularly suitable for the synthesis of nitroaliphatics containing fluorine, which in turn can be used as precursors for the preparation of herbicides (see U.S. Pat. No. 4,533,776).
It is known that 3-fluoro-2-(fluoromethyl)-propene (I) is obtained as an undesirable by-product, as a result of pyrolytic splitting off of hydrogen chloride and formaldehyde, in a yield of only 12.7% when attempts are made to react pentaerythritol-tribromohydrin (III) with potassium fluoride to give the corresponding trifluoro compound (see Bull. Soc. Chim. France, 1953, 123/124). This reaction is illustrated by the following equation (1): ##STR3##
With this synthesis sequence, there is of course no possibility of preparing 3-fluoro-2-(fluoromethyl)-propene (I) on an industrial scale.